**The sum of sine squared plus cosine squared is 1.** While the sine is calculated by dividing the length of the side opposite the acute angle by the hypotenuse, the cosine is calculated by dividing the length of the side that is adjacent to the acute angle by the hypotenuse.

For example, the sine of a 30-degree angle is 1/2 and the cosine of a 30-degree angle is the square root of 3/2. One-half squared is equal to 1/4, and the square of the square root of 3/2 is equal to 3/4. When added together, 1/4 plus 3/4 equals 1.